1. Render the model for comtour layers ... beach, low hills, higher hills, etc.
2. Change that render into a set of masks to use in placing image data in Photopaint.
3. The colour file assigned to the Colour map material.
4. Change the colour image to greyscale and invert for the image file to assign to the Bump map material.

The scale I have in mind would need at least 50 trees or so. And they would be stunted scrub type ... high wind, almost Arctic latitudes. But the rest of the scene , when it happens, will set the scale.

I realise now I need another shade region for the sea to sand zone. Sea colour is wrong but the above was only a check render.